Having said that, since this blog is about melee tactics, I might as well throw in a little something about it from that perspective.
Poles are, in my opinion, the finger in a dike that is built largely of shields and spears. Shields form the foundation that your unit is built off of, spears are the killing machines, and poles fill in the cracks between the two.
The polearm's job is mainly to hang back, watch, and wait for an opportunity. Opportunities present themselves in a couple of manners. As shields that are too far away to hit you, or as opponents who are preoccupied with one of your allies.
90% of your kills will come in one of three fashions:
1) A light, quick stab to the face
2) A hard, heavy stab to the gut on the sword arm side (usually their right) of a sword and shield
3) A hard shot to the left side of their head
If you don't find one of those three shots open, then swing anyway. It will blind them and keep them busy.
By and large your best defense against a sword and shield is going to be to swing at them as you back away and run toward your guys. Once you are with your team, you should be able to find opportunities where you can attack a shiedman who is engaged with another fighter.
If you are in the middle of a static battle, your best bet is usually to stand in the second rank and wait. If the lines press, you need to follow from the second rank and swing over top of the shields.
That's it in a nutshell.